Apparatus of the kind mentioned above are already known, e.g. from the U.S. Pat. Nos. 3,688,743, 3,730,142 and 4,270,489, the German published specification Nos. 2 310 382 and 2 441 936 and the Norwegian patent No. 128 514.
The apparatus according to the U.S. Pat. Nos. 3,688,743, 3,730,142 and 4,270,489 each include a pendulum dependent in the water. A body connected to the pendulum and mounted to cover an opening in a feed container uncovers a part of this opening when the pendulum is displaced by the fish from a straight-down dependent position, such that a given quantity of feed is discharged.
The greatest disadvantage with these apparatus is that a relatively large force is required to swing the pendulum, resulting in that the apparatus can only be used for relatively large fish. If the apparatus are used in conjunction with fish breeding in lakes, rivers or the like, currents and waves also cause the pendulum to be swung with undesired feed discharge as a result.
The apparatus according to the German published specification Nos. 2 310 382 and 2 441 936 include pendulums dependent in water in aquaria. When the pendulums are acted on by fish, a current circuit is closed so that a relay is excited to provide discharge of feed from a container suspended above the water surface.
Even if just as large a force is not required for swinging the pendulums according to both the last-mentioned publications, very small fish cannot achieve this pendulation. Furthermore, the pendulums would be affected by currents and waves, resulting in undesired feed discharge, if the apparatus were used for fish breeding outdoors. Since the contacts included in the current circuit are placed without protection and in the vicinity of the water they are oxidized rapidly, and the operational reliability of the apparatus is lowered. The apparatus according to the Norwegian patent No. 128514 includes a feed container with an opening through which feed is discharged with the aid of a conveyer screw coupled to an electric motor, which is started when a current circuit is closed by a sprung breaker arm being caused to engage a contact when bait attached to a line dependent from an arm is taken by a fish.
This latter apparatus also requires relatively large force, and furthermore the force must be applied in a given direction for the arm to close the circuit. This means that the apparatus cannot be used in breeding smaller fish. If the spring in the breaker arm is selected so that it is very weak, a minor force can indeed cause the circuit to be closed when a smaller fish takes the bait, but the apparatus will be very sensitive to currents, waves and winds at the same time, and can therefore be triggered even when there are no fish in the vicinity of the apparatus. The placing of the contact and breaker arm and their nearness to the water also results in operational problems.